A conventional CRT display which is used in a television set, a personal computer, etc. is provided with knobs for controlling contrast and brightness of images on a screen thereof, so that the quality of the images is improved in accordance with the adjustment of contrast and brightness by use of the knobs.
In recent years, a display apparatus in which the color tone (determined by the color temperature at the state of all white pattern display, and defined "color temperature" hereinafter) is adjusted in addition to the contrast and brightness is required to be put into practical use. In such a display apparatus, a desired color temperature is obtained to provide reddish white, bluish white, etc.
Such demand is high in a display apparatus for an information processing apparatus in which still images are displayed on a screen thereof, although the demand is relatively low in a television set in which motion images are displayed on a screen thereof, so that the color temperature is observed difficult to be due to the motion thereof. In addition, the demand of controlling the color temperature is high, for instance, in a display apparatus of a computer graphics system, an apparel design system, etc., in which the reproducibility of colors is important, because colors are required to be displayed precisely on a screen thereof.
In the conventional display apparatus, the color temperature is adjusted in a manufacturing factory by use of sub-contrast and sub-brightness knobs which are provided in the interior of the display apparatus, so that these knobs are not handled by a user.
However, the conventional display apparatus has disadvantages in that specialized operation and a considerably long time is required in the adjustment of the color temperature in the manufacturing factory. For this reason, even if a color temperature knob which is handled by a user is provided at the exterior of the display apparatus, this is not a practical structure.
In addition, it is considered that the color temperature must be adjusted for plural times, because the color temperature tends to change in a case where contrast and brightness are adjusted, after the color temperature is once adjusted. In other words, the so-called color tracking, in which the color temperature is not changed between before and after the adjustment of contrast and brightness, when the color temperature is once adjusted, is required to be realized in a display apparatus.